The present invention relates generally to vacuum electronic devices, and more specifically the invention pertains to a means for integrating an "intelligent" electronic feedback system into the structure of vacuum electronic devices whose subcomponents are electronically and/or electro-mechanically adaptive. By "vacuum electronic device," is meant any source of microwave (or millimeter-wave) power generation which is driven by electron beams (e-beams).
Vacuum electronic devices which use an integral energetic electron-beam to generate microwave or millimeter-wave radio frequency (rf) power have been in existence in a wide variety of forms since the 1930s. Up to this time, all known vacuum electronic devices have no ability at all to adapt or modify their own operating characteristics. No such devices are manufactured with any ability to sense either their internal states or their output signals. Nor have such devices ever been equipped with on-board microprocessor "brains" which could process sensed data and "act" upon it.
In short, all vacuum electronics to date can only be characterized as "dumb" and unadaptable. The manufacturers of these devices spend large amounts of time in theoretical analysis, subcomponent testing, "cold testing" (i e., testing the beam/rf interaction cavity in the absence of the electron beam), and a painstaking final assembly process during which all components are fitted into the final device to very exact spatial tolerances. This long and tedious process largely explains the high cost ($20,000-$250,000) associated with the completed device. It is also significant to point out that some aspects of the design and fabrication process can still be characterized as a "black art." Senior, experienced engineers are relied upon to use their intuition to finalize some key design parameters without the benefit of thorough physical analysis or understanding. This naturally leads to variations and uncertainty in the final product based upon the skills of the local design and fabrication teams.
Finally, the inability of the devices to modify their internal spatial configurations and/or their electrical operating characteristics necessarily shortens their "shelf-life" and operating lifetime in stressful environments. Vacuum electronics subjected to prolonged storage before use can degrade through such mechanisms as thermionic cathode "poisoning", permanent magnet weakening, and mechanical warpage of critical subcomponents. A self-adaptive device should be able to compensate for some of these flaws to achieve useful operation. Similarly, some devices, particularly those used for military and space applications, are subjected to extremes of temperature and mechanical stress (G-forces). Such conditions can cause an immediate loss of performance and/or permanent damage to the device. The danger of these consequences taking place could be lessened by giving the device the ability to internally compensate for temperature and mechanical stresses. The task of providing a smart adaptive vacuum electronic system is alleviated to some extent, by the systems disclosed in the following U.S. patents, the disclosures of which are incorporated herein by reference:
U.S. Pat. No. 5,208,512 issued to Forster, et al;
U.S. Pat. No. 5,162,965 issued to Milberger, et al;
U.S. Pat. No. 5,124,664 issued to Cade, et al;
U.S. Pat. No. 5,083,097 issued to Bolie;
U.S. Pat. No. 5,079,484 issued to Rambert;
U.S. Pat. No. 4,992,656 issued to Clauser;
U.S. Pat. No. 4,939,331 issued to Berggren, et al;
U.S. Pat. No. 4,933,650 issued to Okamoto;
U.S. Pat. No. 4,873,408 issued to Smith, et al;
U.S. Pat. No. 4,709,215 issued to McClanahan, et al;
U.S. Pat. No. 4,687,970 issued to Musslyn, et al;
U.S. Pat. No. 4,485,349 issued to Siegel, et al;
U.S. Pat. No. 3,866,077 issued to Baker, et al;
U.S. Pat. No. 4,754,239 issued to Sedivec.
The McClanahan et al '215 patent relates to radar transmitters and discloses an attenuation control circuit and a feedback phase control circuit which command digital and analog phase shifters in a travelling wave tube controller.
The Okamoto '650 patent discloses a microwave plasma production apparatus which incorporates a control system comprising a microcomputer.
The Baker et al '077 patent relates to vacuum electronic devices having a valve which may be used to provide feedback from one portion of the emitted electron beam to control the emission control means and reduce noise emitted by the source.
The Bolie '097 patent provides error control loops for pulsed high-power klystrons which automatically "learn" through analysis of past pulse waveform characteristics to properly set the initial condition for a future pulse. Adaptive memory subsystems are described.
The Siegel et al '349 patent relates to a stabilized klystron-based microwave power amplifier system. This patent discloses a microprocessor means which compares a digital signal of actual output power to digital reference signals representative of a desired reference input power level and generates digital correction signals.
The Cade et al '664 patent shows a klystron-type oscillator device having a feedback capability which causes the device to oscillate.
The Forster et al '512 patent relates to a scanned electron cyclotron resonance plasma source wherein a microprocessor controls the frequency of electromagnetic waves emanating from the source of microwaves such as a klystron or a magnetron.
The Rambert '484 patent refers to feedback means in the voltage regulated supply for microwave tubes.
The Clauser '656 patent relates to rotation, acceleration and gravity sensors using quantum-mechanical, matter-wave interferometry with neutral atoms and molecules. The invention allows for compensation of matter-wave path deflections due to inertial effects by different means such as rotationally mounting each interferometer on gimbals or applying additional potentials that introduce defects, and/or retard, and/or accelerate the matter wave propagation. The applied potentials and/or gimbals can then be controlled by a feedback system that maintains null interferometer fringe shifts. Electron beams are disclosed.
The Musslyn et al '970 patent relates to a digital cathode current control loop for controlling the cathode current of a travelling wave tube amplifier.
The Milberger et al '965 patent relates to use of feedbacks and gate reference resistors for microwave tube transmitters.
The Smith et al '408 patent relates to a magnetron with microprocessor based feedback control in the context of microwave oven use. See also the Berggren et al '331 patent.
While the above-cited references are instructive, a need remains to integrate an intelligent electronic feedback system into the structure of vacuum electronic devices whose subcomponents are electronically and electromechanically adaptive. The present invention is intended to satisfy that need.